The present invention relates to a process of manufacturing olefin sulfonate solution containing .alpha.-olefin sulfonates at a high concentration and having a low viscosity.
.alpha.-OLEFIN SULFONATES USEFUL AS THE ACTIVE INGREDIENT OF GRANULAR HEAVY DUTY DETERGENTS, ETC. ARE GENERALLY MANUFACTURED BY SULFONATING .alpha.-OLEFINS HAVING 10 - 20 CARBON ATOMS AND SUBJECTING THE RESULTING SULFONATES TO NEUTRALIZATION AND HYDROLYSIS WITH ALKALI. In this neutralization-hydrolysis process, water is naturally required and, therefore, the olefin sulfonates product is obtained usually in the form of an aqueous solution. As the process of manufacturing a granular heavy duty detergent containing olefin sulfonates, a process has been adapted which comprises preparing a detergent slurry by admixing this olefin sulfonate solution with other active detergent ingredients as occasion demands and further adding thereto a desired builder, and thereafter subjecting said slurry to spray drying, thereby obtaining a granular heavy duty detergent.
In the case of this conventional process, from the view point of productivity, it is profitable to make the concentration of the solid matters in said detergent slurry as high as possible, provided that handling of the slurry is not inconvenient. Besides, depending on the intended use of said slurry, there are some cases wherein a slurry that does not have a low water content is disqualified for economic or technical reasons, and, from the view point of practical application too, a highly concentrated slurry is advantageous.
However, in the case of manufacturing modern heavy duty granular detergents called KONPACTO SENZAI (which means compacted detergent) or NOSHUKU SENZAI (which means concentrated detergent) placed on the market in Japan since 1975, it is very advantageous to make high the concentration of the solid matter in said slurry, namely the concentration of nonvolatile materials such as active ingredient, builder and other additives. This compacted granular heavy duty detergent for heavy duty is, to be precise, a detergent whose bulk density is greater than that of conventional granular detergents (that is, the bulk density of conventional granular detergents is in the range of 0.25 - 0.30 in terms of BD, while in the case of this compacted granular detergent, it is more than 0.34) and the amount of detergent necessary for washing is less than that of conventional detergents. Accordingly, it has an advantage that a substantial reduction of the package cost, transport cost and warehouse charge is possible compared with conventional detergents.
Inasmuch as a detergent slurry is, as stated above, generally prepared by adding a desired builder and other detergent additives to an active ingredient solution, in order to prepare a slurry having high concentration of solid matter, it is necessary to employ an active ingredient solution having a high concentration (or low water content). However, in the case of applying olefin sulfonates as said active detergent ingredient, it has been very difficult to manufacture a low-viscosity active ingredient solution having a good workability by the known methods.
In other words, the conventional olefin sulfonate solutions are, as set for above, manufactured through the process wherein olefin sulfonates are neutralized and hydrolyzed by using the stoichiometric alkaline material in an amount necessary for neutralizing and hydrolyzing said olefin sulfonates or a slight excess amount of said alkaline material (typically caustic soda), in the form of an aqueous solution thereof having a concentration of about 7 - 8%. However, in order to obtain a low-viscosity olefin sulfonate solution having a good workability so as not to cause inconvenience in preparing a detergent slurry, the limit of the water content thereof is about 60%, and it is impossible to make the water content below this limit. An olefin sulfonate solution obtained by the conventional process is too high in water content for use as the active ingredient solution used in manufacturing a compacted detergent.
As the means for lowering the water content of an olefin sulfonate solution from common sense, it is conceivable to reduce the amount of the aqueous solution of alkali used in the neutralization-hydrolysis step and to concentrate or dry the olefin sulfonate solution per se. Neither of these procedures can provide an olefin sulfonate solution which fits the purpose of the present invention.
In this connection, according to the process of reducing the amount used of the aqueous alkali solution by increasing the concentration of aqueous alkali solution for use in neutralization-hydrolysis as adopted in the conventional process, the amount of water in the mixture of sulfonates and alkaline material inevitably becomes insufficient so that it is difficult to bring the sulfonates into uniform contact with the alkaline material so as to effect sufficient neutralization and hydrolysis; and even if said neutralization and hydrolysis are effected sufficiently, the resulting product will be of high viscosity and it may gel.
On the other hand, drying or concentrating an olefin sulfonate solution containing about 60% of water as manufactured through the conventional process is uneconomical inasmuch as it necessitates the additional step of drying or concentrating, and not only that, there is a fear that scorching will occur during drying and the viscosity of the solution will increase during concentrating. Therefore, neither the drying step or the concentrating step is advisable.
To sum up, as long as the conventional neutralization-hydrolysis process is followed, it is substantially unfeasible to manufacture, in an economic and industrially satisfactory manner, an olefin sulfonate solution having a low viscosity and which does not interfere with the preparation of a detergent slurry.